Van der Hoeven J H, Lange F
Department of Clinical Neurophysiology, University Hospital Groningen, The Netherlands.
J Appl Physiol (1985). 1994 Aug;77(2):802-6. doi: 10.1152/jappl.1994.77.2.802.
Muscle fiber conduction velocity (MFCV) and surface electromyographic parameters were studied in the brachial biceps muscle of healthy males during voluntary intermittent isometric contractions at 50% of maximum force. Recovery in the following 15 min was then observed. The measurements were performed during duty cycles of 33, 25, and 20%. The main finding was a supernormal MFCV during the exercise phase when the duty cycle was 25 and 20%. The level continued to increase during the recovery phase. During the exercise phase when the duty cycle was 33%, the MFCV decreased slightly (suggesting that the local anaerobic threshold had been surpassed) but increased during recovery to supernormal values. The ratio of median frequency to MFCV was constant during all experiments, indicating that the changes in median frequency reflect those in MFCV. We suggest that the supernormal MFCV was due to a combination of altered membrane properties, muscle fiber swelling, and temperature increase and hypothesize that the changes of electrical properties formed part of an adaptive mechanism of the muscle fiber membrane during exercise. In that respect, the increase of the MFCV could be a component of the well-known warm-up effect.
在健康男性肱二头肌进行最大力量50%的自愿间歇性等长收缩期间，研究了肌纤维传导速度（MFCV）和表面肌电图参数。随后观察接下来15分钟内的恢复情况。测量在占空比为33%、25%和20%时进行。主要发现是，当占空比为25%和20%时，运动阶段MFCV出现超常现象。在恢复阶段该水平持续升高。当占空比为33%时，运动阶段MFCV略有下降（表明局部无氧阈值已被超过），但在恢复过程中升至超常值。在所有实验中，中位频率与MFCV的比值恒定，表明中位频率的变化反映了MFCV的变化。我们认为，超常的MFCV是由于膜特性改变、肌纤维肿胀和温度升高共同作用的结果，并推测电特性的变化是运动期间肌纤维膜适应性机制的一部分。在这方面，MFCV的增加可能是众所周知的热身效应的一个组成部分。
